Cooling system for a dental handpiece

ABSTRACT

A dental handpiece including a handle, a shank and a head is disclosed for conveying a cooling stream of air to a workpiece. The stream of air is conveyed through a passageway in the dental handpiece to a cap in the head. The cap includes a collection chamber for receiving and distributing the stream of air. The air within the collection chamber is forced out through an axially disposed aperture within the cap and internal to the head. The end of a hollow burr, the burr being rotatably mounted within the head, communicates with the collection chamber via an apertured resilient coupling. Thereby, the air forced out of the collection chamber, flows through the coupling and into the hollow burr. Thence, the air flows through the burr to the working portion thereof and cools the working portion as well as the workpiece in proximity to the working portion.

United States Patent 1 1 1 ,778,904 Melde Dec. 18, 1973 1 COOLING SYSTEM FOR A DENTAL HANDPIECE Chris R. Melde, 7755 Foothill Dr.,

Primary Examiner-Louis G. Mancene Assistant Examiner.l. Q. Lever AttorneyWilliam C. Cahill et a1.

A dental handpiece including a handle, a shank and a head is disclosed for conveying a cooling stream of air to a workpiece. The stream of air is conveyed through a passageway in the dental handpiece to a cap in the head. The cap includes a collection chamber for receiving and distributing the stream of air. The air within the collection chamber is forced out through an axially disposed aperture within the cap and internal to the head. The end of a hollow burr, the burr being rotatably mounted within the head, communicates with the collection chamber via an apertured resilient coupling. Thereby, the air forced out of the collection chamber, flows through the coupling and into the hollow burr. Thence, the air flows through the burr to the working portion thereof and cools the working portion as well as the workpiece in proximity to the working portion.

10 Claims, 2 Drawing Figures PATENIEUBEB 18 I975 II, E... i--

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COOLING SYSTEM FOR A DENTAL HANDPIECE The present invention relates to dental handpieces, and more particularly, to dental handpieces incorporating a coolant flowing through the burr to a workpiece.

Dental handpieces are generally used to perform both grinding and cutting operations upon a workpiece. Either of these operations generate a substantial amount of heat. Where the workpiece is a tooth or a filling within a tooth in a patients mouth, the heat generated may be painful as well as uncomfortable. Where the dental handpiece is used upon workpieces outside of a patients mouth, such as braces, dentures, and splints, the heat generated may deleteriously affect the materials being worked upon.

To circumvent the problems attendant the generated heat, various means have been developed to reduce or dissipate the generated heat. In one type of an airdriven handpiece, water is pumped through the dental handpiece, into a hollow burr and flows from the working portion thereof onto the workpiece. The use of water is satisfactory in several respects in that it is easily obtainable, requires no special containers and does not quickly corrode the working elements of the dental handpiece is properly channeled. However, two major problems exist when water is used. First, the channeling of the water from the dental handpiece and into the hollow burr requires specially designed elements to prevent the water from entering the bearings supporting the rotating burr and removing or limitingthe effectiveness of the bearing lubricant. Second, although the water does not usually affect the properties of the workpiece, the presence of water, whether in solid form or as a mist, tends to obscure the workpiece from view. Thereby, the amount of work that can be performed by the burr is limited be required periodic mopping or draining of the water. A coolant such as air does not present quite the same problems as water, but there are other attendant difficulties. First, the mass of the air, or some other gas, is relatively low. The low mass of the gas tends to permit the gas to be easily deflected by extraneous forces adjacent the hollow burr. The rotating hollow burr immediately subjects the low mass of gas to substantially different forces as the gas enters the hollow portion of the burr than are present outside of the burr. The net effect of the forces acting upon the gas within the burr is that of inhibiting the flow of gas through the burr.

To solve the above-enumerated problems in injecting a flow of air into a hollow burr, various coupling devices have been developed to channel the air from a non-rotating part within the head to the rotating hollow burr. One of the most common of these couplings is that of mounting a conduit adjacent the head of the dental handpiece with the nozzle in axial alignment with the hollow burr. A stream of air is forced through the conduit and the nozzle and into the hollow portion of the burr. A disadvantage of this type of coupling is that presently used and available dental handpieces must be substantially and expensively modified to incorporate the conduit and nozzzle. In another type of coupling, the hollow burrs are modified by adding one or more radial passageways between the hollow portion of the burr and the cylindrical surface of the burr. The head of the dental handpiece is modified to permit a coupling to be inserted therein, which coupling includes a collection chamber. A dental handpiece is also modified to provide a source of air flow through the dental handpiece to the collection chamber of the coupling. This type of coupling has one distinct advantage but suffers from several disadvantages. The advantage obtained is that of generally not requiring any'extensive modification to the head of the dental handpiece. In most existing dental handpieces, the bearing housing and turbine connected to the hollow burr need only be modified to accept the addition of the above-described coupling. The additional source of air flow connected to the coupling can be easily and simply accommodated within the shank and handle of existing dental handpieces. The primary disadvantage of this coupling is that there is at best an inefficient flow of air through the radial passageways into the hollow portion of the burr and thence to the working portion of the burr. Centrifugal forces act upon the air attempting to flow through the radial passageways and establish a back pressure. In addition, the abrupt change in direction of flow of the air from the radial passageway to the hollow portion of the burr causes a pressure drop, which pressure drop reduces the rate of flow. The non-working end of the hollow burr must, of course, be sealed to prevent air flow therethrough rather than through the working portion. The resultant seal invariably leaves a small air chamber intermediate the radial passageways and the seal itself. A pressure buildup tends to occur within this chamber and further inhibits the flow of air from the radial passageway into the hollow portion of the burr. Thus, the above-described coupling is mechanically simple and relatively inexpensive to incorporate but has adverse effects on the effectiveness of the air flow through the hollow burr.

It is therefore a primary object of the present invention to provide apparatus for conveying a stream of air through a hollow burr within a dental handpiece.

Another object of the present invention is to provide apparatus which may be incorporated in existing dental handpieces for conveying a stream of air through a hollow burr.

Yet another object of the present invention is to provide a means for coupling an air flow source within the head ofa dental handpiece to the end of a hollow burr.

The present invention may be described with more specificity and clarity with reference to the following drawings, in which:

FIG. 1 illustrates a dental handpiece incorporating the present invention.

FIG. 2 illustrates a cross sectional view of a head of an existing dental handpiece incorporating the present invention.

Referring to FIG. 1, there is shown a dental handpiece I, representative of presently available and used dental handpieces. The dental handpiece 1 includes a handle 2 for gripping the dental piece and a shank 3 for securing the cylindrically shaped head 4 to the handle at a comfortable angle. Head 4 housesan air turbine which rotatably drives a hollow burr 7. A plurality of air tubes 5 extend through handle 2 and shank 3 to head 4, one of which, when connected to an air pressure source, drives the turbine. Another of the tubes 5 provides a source of air flow to head 4, which air flow is conveyed through hollow burr 7, as will be explained in more detail below. A cap 6, threadedly secured within head 4, is similar in external dimensions to existing caps and acts as a replacement therefor. Cap 6 seals one end of the cylindrical cavity disposed within head 4.

Referring to FIG. 2, there is shown a detailed cross sectional view of head 4, cap 6 and a part of shank 3. Head 4 is generally cylindrical and normally secured to shank in a right angled relationship. A cylindrical cavity, defined by side wall 8, is axially disposed within head 4.

Shank 9 of burr 7 is frictionally fitted within a hollow shaft 10. The relationship between burr 7 and shaft 10 should be such that the burr may be removed and inserted within the shaft without undue physical strain, yet provide sufficient friction therebetween, whereby rotation of the shaft will cause the burr to rotate. Shaft 10 is positioned within the cylindrical cavity in head 4 by two rotary bearings 11 and 12. These bearings may be of any of several different types; however, it has been found that caged ball bearings rotating within an inner and an oujer race have proven quite satisfactory.

I Disposed between ball bearings 1 l and 12 and frictionally fitted to shaft 10 is an air turbine 13.

The configuration of turbine 13 may be of any one of several known types; however, a configuration which is particularly suitable for dental handpieces is that known as a bucket turbine. That is, the cylindrical surface of turbine 13 has a plurality of depressions or buckets 14 radially disposed therein. A stream of fluid, striking these buckets l4, imparts a force, which. force causes theturbine torotate or spin.

The stream of fluid, which is usually an air stream,in introduced to the dental handpiecethrough one of the tubes 5 in handle 2. The air stream flows within the tube 5' through handle 2 and shank 3 to orifice 15 disposed in side wall 8. The air stream flows out of orifice 15 and strikes buckets l4. Rotation of turbine 13 is effected by the force of the steam of air striking the buckets 14.

The inflowing air, operating upon turbine 13, flows circumferentially about the turbine to an inlet 16. inlet 16 is disposed within side wall 8 and represents the inlet to exhaust passageway 17. Exhaust passageway 17 exztends through shank 3 and handle 2. In this manner, the exhaust air is conveyed away from the head 4.

1n the standard dental handpieces, the cylindrical cavity within the head is generally partially enclosed at the lower end by an apertured circular plate, such as plate 18 threadedly engaging side wall 8, and sealed at the upper end by a cap, such as cap 6 threadedly engaging side wall 8.

ln the present invention, apparatus is disclosed, which, when used in conjunction with a simple modification to the handle 2, shank 3 and head 4, permits the directing of a stream of air through hollow burr 7 to the workpiece. The handle 2, shank 3 and head 4 are rnoditied to include a passageway 19 extending therethrough. Generally, the major modification to dental handpieces is that of drilling a passageway 19' from the upper part of head 4'to the junction between head 4 and shank 3. The remaining portion of passageway 19 may comprise a piece of tubing secured to the drilled passageway 19' and lodged within shank 3 and handle 2. One of the tubes 5 (as shown in H6. 1) is representative of the tube defining passageway 19 extending from handle 2. The upper end of drilled passageway 19' communicates with the cylindrical cavity within head 4 in proximity to the upper portion of internal threads 20, the latter being disposed within side wall 8.

Cap 6 includes a radial flange 21 for sealably engaging upper surface 22 of head 4. A hollow threaded boss 23 of cap 6 engages threades 20, whereby cap 6 can be screwed into and out of head 4. A recess 24 is disposed about boss 23 immediately adjacent radial flange 21. When cap 6 is secured within head 4, recess 24 is aligned with the orifice of passageway 19'' A plurality of radial passageways 25 extend from recess 24 to the hollow portion within boss 23. The internal side wall 26 of boss 23 is at least partially threaded to threadedly receive an apertured circular plate 27. Aperture 28 of plate 27 is centrally disposed therein and in approximately axial alignment with hollow burr 7. Thus, an air collection chamber is formed within cap 6 by the com bination of hollow boss 23 and plate 27.

An axially oriented circular recess 29 is disposed within plate 27 and faces the end of burr 7. A coupling 30, inlcudes a protrusion 31, the latter fitting within recess 29, and a central recess 32, the latter fitting about the end 33 of burr 7. A passageway 34 extends through the coupling from protrusion 31 to recess 32. it has been found through experimentation that the best results may be obtained if coupling 30 is of somewhat flexible resilient material. The flexible and resilient features permit some degree of misalignment between recess 29 and end 33 of burr 7 without seriously affecting the operation of the dental handpiece. 1

In operation, the present invention may be described as follows. A stream of air, introduced to the dental handpiece through one of tubes 5, flows through tube 5 and strikes each of the buckets 14, in order. The force of the air flow causes turbine 13 to rotate, which rotation in turn rotates burr 7. The air flows partially about turbine 13 to inlet 16 of exhaust passageway 17. Simultaneously, another of tubes 5 provide an air flow input to passageway 19. The air flows through passageways 19 and 19 to the annular cavity defined by recess 24 and threads 20. As pressure builds up within this annular cavity, the air will flow through passageways 25 into the hollow portion of boss 23. In turn, the air pressure will build up within the boss 23 until the air flows out through aperture 28. Passageway 34, being aligned with aperture 28 due to the mating of protrusion 31 within recess 29, further directs the air flow from within cap 6. Hollow burr 7 is aligned with passageway 34 by the mating of end 33 with recess 32. Thus, the air flowing into the hollow portion of cap 6 will flow out therefrom through aperture 28, through passageway 34 and into the hollow porion of burr 7. There will, of course, be some leakage intermediate cap 6 and coupling 30 as well as between coupling 30 and burr 7 as these points of contact are not specifically intended to be wholly airtight. The points of contact are simply snug but yet not so snug as to cause undue friction between the non-rotating elements and the rotating burr. The amount of air leakage is, at most, a small percentage of the total air flow and thus, does not seriously or deleteriously affect the total air flow through burr 7 to the workpiece. The total amount of air flow can, of course, be regulated by regulating means secured to either tubes 5 or a valve disposed within passageway 19.

As discussed above, the above-described means for effecting an air flow through a hollow burr can be incorporated into most presently used dental handpieces without extensive or expensive modifications. The axial length of the cap and coupling 30 must, of course, be suitably tailored to fit within the various sized heads so as not to require displacement of a turbine nor of its associated air stream. As most presently used heads are of solid material except for the inlet and exhaust passageways for the turbine, substantial latitude is available in the alignment and drilling of passageway 19. The handle and shank of most dental handpieces are generally hollow, thus, passageway 19 can simply be a piece of copper tubing secured to one end of passageway 19 and extending through shank 3 and handle 2.

While the principles of the invention have now been made clear in an illustrative embodiment, there will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, the elements, materials, and components, used in the practice of the invention which are particularly adapted for specific environments and operation requirements without departing from those principles.

I claim:

1. In a dental handpiece having a handle, a shank, a head including a cylindrical cavity therein, power transmission means disposed within the cavity, and a hollow burr engaged to the power transmission means and extending from one end of the head, the improvement comprising:

a. conveying means for transporting a flow of air to another end of the head;

b. a cap having a centrally disposed apertured cavity secured to said other end for covering one end of the cylindrical cavity within the head;

c. transmission means for transmitting the flow of air from said conveying means to said apertured cavity within said cap; and

d. coupling means disposed intermediate said cap and the hollow burr for providing an air passageway from said apertured cavity within said cap to the passageway within the hollow burr, whereby a flow of air is conveyed from the dental handpiece through the hollow burr.

2. The dental handpiece as set forth in claim 1, wherein said conveying means terminates at an orifice disposed in the wall of the cylindrical cavity within the head in proximity to said other end of the head.

3. The dental handpiece as set forth in claim 2,

wherein said cap includes a hollow boss for engaging the wall of the cylindrical cavity within the head to a depth greater than the depth of said orifice from said other end of the head.

4. In a dental handpiece having a handle, a shank, a head including a cylindrical cavity therein, power transmission means disposed within the cavity, and a hollow burr engaged to the power transmission means and extending from one end of the head, the improvement comprising:

a. conveying means for transporting a flow of air to another end of the head, said conveying means terminating at an orifice disposed in the wall of the cylindrical cavity in proximity to said other end of the head;

b. a cap having a centrally disposed apertured cavity secured to said other end for covering one end of the cylindrical cavity within the head, said cap including a hollow boss for engaging the wall of the cylindrical cavity within the head to a depth greater than the depth of said orifice from said other end of the head;

c. power transmission means for transmitting the flow of air from said conveying means to said apertured cavity within said cap, said power transmission means including an annular recess about said boss in proximity to said orifice and a plurality of passageways extending from said recess to said apertured cavity within said cap, and

d. coupling means disposed intermediate said cap and the hollow burr for providing an air passageway from said apertured cavity within said cap to the passageway within the hollow burr, whereby a flow of air is conveyed from the dental handpiece through the hollow burr.

5. The dental handpiece as set forth in claim 4, wherein said cap threadedly engages said other end of the head.

6. The dental handpiece as set forth in claim 4, wherein said apertured cavity within said cap is formed by a circular apertured plate threadedly engaging the internal surfaces of said hollow boss.

7. The dental handpiece as set forth in claim 6, wherein the outer side of said plate includes a recess about the aperture extending through said plate.

8. The dental handpiece as set forth in claim 6, wherein said coupling means includes an apertured protrusion for mating with said recess in said plate.

9. The dental handpiece as set forth in claim 8, wherein said coupling further includes a recess communicating with said apertured protrusion and mating with the end of the hollow burr.

10. The dental handpiece set forth in claim 1, wherein said conveying means is internal to the dental 

1. In a dental handpiece having a handle, a shank, a head including a cylindrical cavity therein, power transmission means disposed within the cavity, and a hollow burr engaged to the power transmission means and extending from one end of the head, the improvement comprising: a. conveying means for transporting a flow of air to another end of the head; b. a cap having a centrally disposed apertured cavity secured to said other end for covering one end of the cylindrical cavity within the head; c. transmission means for transmitting the flow of air from said conveying means to said apertured cavity within said cap; and d. coupling means disposed intermediate said cap and the hollow burr for providing an air passageway from said apertured cavity within said cap to the passageway within the hollow burr, whereby a flow of air is conveyed from the dental handpiece through the hollow burr.
 2. The dental handpiece as set forth in claim 1, wherein said conveying means terminates at an orifice disposed in the wall of the cylindrical cavity within the head in proximity to said other end of the head.
 3. The dental handpiece as set forth in claim 2, wherein said cap includes a hollow boss for engaging the wall of the cylindrical cavity within the head to a depth greater than the depth of said orifice from said other end of the head.
 4. In a dental handpiece having a handle, a shank, a head including a cylindrical cavity therein, power transmission means disposed within the cavity, and a hollow burr engaged to the power transmission means and extending from one end of the head, the improvement comprising: a. conveying means for transporting a flow of air to another end of the head, said conveying means terminating at an orifice disposed in the wall of the cylindrical cavity in proximity to said other end of the head; b. a cap having a centrally disposed apertured cavity secured to said other end for covering one end of the cylindrical cavity within the head, said cap including a hollow boss for engaging the wall of the cylindrical cavity within the head to a depth greater than the depth of said orifice from said other end of the head; c. power transmission means for transmitting the flow of air from said conveying means to said apertured cavity within said cap, said power transmission means including an annular recess about said boss in proximity to said orifice and a plurality of passageways extending from said recess to said apertured cavity within said cap, and d. coupling means disposed intermediate said cap and the hollow burr for providing an air passageway from said apertured cavity within said cap to the passageway within the hollow burr, whereby a flow of air is conveyed from the dental handpiece through the hollow burr.
 5. The dental handpiece as set forth in claim 4, wherein said cap threadedly engages said other end of the head.
 6. The dental handpiece as set forth in claim 4, wherein said apertured cavity within said cap is formed by a circular apertured plate threadedly engaging the internal surfaces of said hollow boss.
 7. The dental handpiece as set forth in claim 6, wHerein the outer side of said plate includes a recess about the aperture extending through said plate.
 8. The dental handpiece as set forth in claim 6, wherein said coupling means includes an apertured protrusion for mating with said recess in said plate.
 9. The dental handpiece as set forth in claim 8, wherein said coupling further includes a recess communicating with said apertured protrusion and mating with the end of the hollow burr.
 10. The dental handpiece as set forth in claim 1, wherein said conveying means is internal to the dental handpiece. 